This invention relates to transformers with a controlled variable output and more particularly to transformers that can automatically maintain constant power from the secondary with a fluctuating power supply to the primary and vary the power from the secondary with a constant or variable power input to the primary. This invention also relates to an invertor transformer reference; Invertor Systems Utilizing Inductive or Capacitive Reactance, Ser. No. 07/775,293, filed Oct. 8, 1991, and to rotating field or induction motor speed or torque control. Many variable power transformers are currently in use and consist of different taps on the secondary coil or a sliding tap that can intersect various positions on the secondary windings. These transformers have either wide range steps or very minor adjustments and are not suitable for micro/macro adjustments in power. Another variable power transformer device consists of a moveable core inside of primary and secondary windings thereby changing flux linkages between primary and secondary windings. This transformer design does not supply a continuous ferro-magnetic path and lends itself to excessive leakage. Another transformer device called a magnetic modulator, U.S. Pat. No. 2,774,057, changes the flux linkage in the core by utilizing a sliding bar. This system would be very inefficient as it would not utilize ferromagnetism. Another transformer Pat. No. 3,716,719 does provide for controlled leakage (bypass) of the magnetic flux and electro magnetically functions well. This transformer, due to the bypass design, would have difficulty in micro adjustment and also would have excessive loads on the bearing surfaces due to the unbalanced forces in the magnetic field. The bearing surfaces on this transformer would abrade very rapidly.